Quantum Cloning Of Continuous Variable Coherent States

It is impossible to copy (or clone) an unknown quantum state perfectly. This is one of the basic rules governing the quantum physics, and that is no-cloning theorem. Many experiments that perform the optimal approximate cloning have been completed. The quantum cloning machines are very important tools in the research of many tasks such as state estimation and eavesdropping on quantum cryptography. Studies on quantum cloning were at first motivated on account of extensive application of the quantum information. In recent years, it has been shown that quantum cloning plays an extremely important role in the quantum information. Especially the research for quantum cloning of continuous variable coherent state, is playing a crucial role in some work such as improving some quantum computational tasks and eavesdropping for quantum key distribution scheme. Therefore, the research for quantum cloning of continuous variables have a historic significance.This paper deals with the study on the quantum cloning of continuous variable coherent state, and the main contents are as follows:1. The theoretical research about quantum teleportation and quantum cloning of continuous variable coherent state. First we introduced the principles, characteristics, and development history of the quantum teleportation and quantum cloning, then theoretically analysed experimental solutions of1(?)2quantum cloning of continuous variable coherent states using simple beam splitters and homodyne detection, and discussed quantum cloning experimental scheme through introducing the nondegenerate optical parametric amplifiers (NOPA) which is used to produce EPR entangled source filling vacuum channel.2. The experimental study on quantum cloning of continuous variable coherent states. First we successfully completed the continuous variable coherent states1(?)2quantum cloning using simple beam splitters and homodyne detection by the electronic feedback technology and optical translation means transform, and draw the conclusion that the fidelity is beyond classical limit. Then the quantum cloning scheme through introducing the nondegenerate optical parametric amplifiers (NOPA) which is used to produce EPR entangled source filling vacuum channel is underway.